This invention relates to an electronic musical instrument and, more particularly, to prevention of noise in an electronic musical instrument.
There has been known an electronic musical instrument which has tone production channels smaller in number than a total number of keys provided in the keyboard, generates, channel by channel vibratory musical tone signals for keys which have been assigned to the respective channels and controls amplitude envelopes the tone signals with respect to each of the channels in accordance with depression (key-on) and release (key-off) of the keys thereby to produce tones corresponding to the depressed keys.
In this type of electronic musical instrument, tone signals tend to remain existing in a stage prior to an envelope imparting circuit even after completion of the decay of the amplitude envelope after the key-off, and this causes undesirable occurrence of idling noise leakage noise.
It is, therefore, an object of the invention to effectively prevent occurrence of such noise in an electronic musical instrument.
It is another object of the invention to provide an electronic musical instrument capable of preventing noise by inhibiting, channel by channel, generation of a tone signal of the channel upon lapse of a predetermined time after the key is released. For achieving this object, key-off of the key assigned to each channel is detected with respect to each channel, a counting circuit is operated in accordance with the detection of key-off and, when the count of the counting circuit has reached a certain value, generation of the tone signal thereafter is inhibited. As the counting circuit for the abovementioned inhibition a counting circuit for controlling an amplitude envelope of the musical tone is used commonly whereby the circuit design is simplified.